A standard subcaliber projectile has a projectile body normally of a relatively hard armor-piercing material and a drive cage or sabot surrounding this body. The projectile body is of a diameter or caliber substantially smaller than the barrel from which the projectile is fired, and the sabot is of substantially larger diameter and fits complementarily in the barrel of the gun from which the projectile is fired. The sabot serves to transmit the force of the propellant to the projectile body, and is constructed to separate from the body after leaving the muzzle so that the body presents substantially less air resistance. Thus a subcaliber projectile can be fired at extremely high muzzle velocities for good armor-piercing capacities and long range.
The separation of the sabot from the body must be uniform so that the body is not deflected from its intended trajectory. If, for instance, a piece of the sabot remains stuck to the body on the underside thereof after the remaining pieces of the sabot separate, the aerodynamics of the flight of the projectile body will be changed to cause it to fall short of its target. At the worst the projectile body can be set tumbling, making it largely ineffective.
In Belgian Pat. No. 754,801 the sabot is spool shaped and formed of two or three identical sector segments forming a cylindrical passage closely surrounding the projectile body and centered of course on the axis defined by this body. Somewhat ahead in the normal flight direction of the projectile of the extreme rear end of the sabot the projectile body is formed with a radially outwardly open semicircular-section groove in which complementary parts or formations of the sabot segments fit. This groove is provided as far forward on the projectile body as possible to prevent crushing of the projectile body, its function being to transmit axial forces from the propellant to the projectile body. On leaving the muzzle of the barrel the rings holding the sabot segments self-destruct, permitting these segments to separate radially outward. As soon as the radially inwardly projecting formations of the segments and the groove separate completely, the segments fall back away from the projectile body.
In U.S Pat. No. 2,775,943 of Eksergian the sabot is joined to the projectile body by engagement of a radially inwardly projecting ridge in a complementary outwardly open groove. Once again this arrangement uses radial separation of the sabot from the projectile. The interfitting groove and ridge are well forward of the rear end of the sabot so if the segments thereof are levered out with their front ends separating from the projectile body while their rear ends remain in contact therewith, as soon as the groove and ridge pull apart there will be axial sliding and general disengagement. As a result this system, like that of the above-discussed Belgian patent, will not ensure rapid and even separation of the sabot segments from the projectile body, and in fact will allow them to slide back on it once they are separated. Thus lateral deflection of the projectile body by the separating sabot is likely.
Similarly, U.S. Pat. Nos. 3,620,167 and 4,362,107 both of Romer have arrangements wherein the front part of the sabot is axially forwardly and radially inwardly concave to act as an air scoop so that trapped air drives the front ends of the sabot segments radially outward. In this arrangement the sabot segments are adhered to a sealing disk that is fixed to the projectile, so that once again these sabot segments can relatively easily interfere with the projectile body during separation and deflect it from its trajectory.